docs(readme): make the top-level README sample runnable and safe

README.md

@@ -34,7 +34,7 @@ from runpod import App, Model, NetworkVolume, Secret
 
 app = App("inference")
 
-models = NetworkVolume("models", size=100)
+checkpoints = NetworkVolume("checkpoints", size=100)
 llama = Model("meta-llama/Llama-3.1-8B-Instruct")
 
 
@@ -44,31 +44,46 @@ llama = Model("meta-llama/Llama-3.1-8B-Instruct")
     gpu="H100",
     workers=(0, 3),
     dependencies=["vllm"],
-    mounts={"/runpod-volume": models},
     model=llama,
     env={"HF_TOKEN": Secret("hf-token")},
 )
 def chat(prompt: str):
     import vllm
 
     llm = vllm.LLM(model=str(llama.path))   # weights already on disk
-    return llm.generate(prompt)
+    result = llm.generate([prompt])[0]
+    return result.outputs[0].text           # results must be JSON values
 
 
 # one ephemeral pod per call: provisions, runs to completion, terminates
-@app.task(gpu="H100", gpu_count=2, mounts={"/models": models})
+@app.task(gpu="H100", mounts={"/checkpoints": checkpoints})
 def finetune(steps: int = 1000):
-    ...
-    return {"loss": final_loss}
+    if steps < 1:
+        raise ValueError("steps must be a positive integer")
+
+    import torch
+
+    model = torch.nn.Linear(1, 1).cuda()
+    optimizer = torch.optim.SGD(model.parameters(), lr=0.05)
+    x = torch.randn(1024, 1, device="cuda")
+    y = 3 * x + 1
+    for _ in range(steps):
+        loss = ((model(x) - y) ** 2).mean()
+        optimizer.zero_grad()
+        loss.backward()
+        optimizer.step()
+    torch.save(model.state_dict(), checkpoints.path / "model.pt")
+    return {"loss": loss.item()}
 
 
 @runpod.local_entrypoint
 def main():
     print(chat.remote("why is the sky blue?"))   # blocks for the result
-    job = finetune.spawn(steps=500)              # fire and forget -> Job
+    print(finetune.remote(steps=500))            # pod terminates on return
 ```
 
 ```bash
+rp secret add hf-token  # store your Hugging Face token once
 rp flash dev main.py    # live dev session: edit, re-run, logs stream back
 rp flash deploy         # deploy production endpoints
 ```

tests/test_readme_example.py

@@ -0,0 +1,97 @@
+"""The README's Example section must stay valid code the SDK accepts.
+
+The sample is the first thing new users copy, so these tests check that it
+references only names it defines, that app discovery accepts it, and that a
+synchronous entrypoint never spawns a task it cannot wait on.
+"""
+
+import ast
+import builtins
+import re
+import symtable
+from pathlib import Path
+
+from runpod.apps.discovery import discover_apps
+
+README = Path(__file__).resolve().parent.parent / "README.md"
+EXAMPLE_HEADING = "## Example"
+PYTHON_BLOCK = re.compile(r"```python\n(.*?)```", re.DOTALL)
+
+
+def _example_source() -> str:
+    text = README.read_text(encoding="utf-8")
+    _, _, section = text.partition(EXAMPLE_HEADING)
+    match = PYTHON_BLOCK.search(section)
+    assert match, "README Example section has no python code block"
+    return match.group(1)
+
+
+def _module_bindings(table: symtable.SymbolTable) -> set:
+    return {
+        sym.get_name()
+        for sym in table.get_symbols()
+        if sym.is_assigned() or sym.is_imported()
+    }
+
+
+def _undefined_globals(source: str) -> set:
+    top = symtable.symtable(source, "README example", "exec")
+    known = _module_bindings(top) | set(dir(builtins))
+    undefined = set()
+
+    def visit(table: symtable.SymbolTable) -> None:
+        for sym in table.get_symbols():
+            if sym.is_referenced() and sym.is_global() and sym.get_name() not in known:
+                undefined.add(sym.get_name())
+        for child in table.get_children():
+            visit(child)
+
+    visit(top)
+    return undefined
+
+
+def _decorator_attr(node: ast.expr) -> str:
+    target = node.func if isinstance(node, ast.Call) else node
+    return target.attr if isinstance(target, ast.Attribute) else ""
+
+
+def test_example_references_only_defined_names():
+    assert _undefined_globals(_example_source()) == set()
+
+
+def test_example_is_accepted_by_app_discovery(tmp_path):
+    sample = tmp_path / "main.py"
+    sample.write_text(_example_source(), encoding="utf-8")
+
+    apps = discover_apps(sample)
+
+    assert len(apps) == 1
+
+
+def test_sync_entrypoint_does_not_spawn_tasks():
+    """A spawned task keeps its pod until awaited, which sync code cannot do."""
+    tree = ast.parse(_example_source())
+    functions = [n for n in tree.body if isinstance(n, ast.FunctionDef)]
+    tasks = {
+        fn.name
+        for fn in functions
+        if any(_decorator_attr(d) == "task" for d in fn.decorator_list)
+    }
+    entrypoints = [
+        fn
+        for fn in functions
+        if any(_decorator_attr(d) == "local_entrypoint" for d in fn.decorator_list)
+    ]
+
+    spawned = {
+        call.func.value.id
+        for fn in entrypoints
+        for call in ast.walk(fn)
+        if isinstance(call, ast.Call)
+        and isinstance(call.func, ast.Attribute)
+        and call.func.attr == "spawn"
+        and isinstance(call.func.value, ast.Name)
+    }
+
+    assert tasks, "expected the example to define at least one task"
+    assert spawned & tasks == set()